The present invention relates to an adaptive cruise control (ACC) system for an automotive vehicle, and more particularly to an ACC system which controls a driving force and/or braking force of the vehicle so as to bring an inter-vehicle distance between a preceding vehicle and a host vehicle closer to a target inter-vehicle distance.
A typical ACC system is arranged to detect an inter-vehicle distance and to control a vehicle speed or driving/braking force so as to bring the inter vehicle distance closer to a target value. Such an ACC system employs one of an A-type method of employing a vehicle-speed sensor and generating a vehicle speed command and a B-type method of directly calculating the driving force command. The A-type method can provide an inter-vehicle distance control system where the affect of disturbance is eliminated by a robust design of a vehicle speed control system. However, this A-type method is required to further improve a control accuracy under an extremely low speed region. On the other hand, the B-type method can accurately perform the control under the low speed region, but it is required to simultaneously satisfy riding comfort and robustness against disturbances. The inventors of the present invention have proposed an ACC system which employs both of the A-type method adapted under a high-speed region and the B-type method adapted under a low-speed region.
However, this ACC system is further required to improve the responsibility of the ACC under a low-speed region against the increase of load to the system.
It is therefore an object of the present invention to provide an improved adaptive cruise control system which enables a controlled vehicle (host vehicle) to accurately execute a following control in the whole vehicle speed region including an extremely low speed region without adding an inter-vehicle distance control system for a low vehicle speed region.
An adaptive cruise control (ACC) system according to the present invention is installed to a host vehicle and comprises a vehicle speed detector detecting a vehicle speed of the host vehicle, a distance detector detecting an inter-vehicle distance between a preceding vehicle and the host vehicle, a driving/braking force generator generating driving/braking force according to a signal indicative of a target driving torque, and a controller connected to the vehicle speed detector, the distance detector and the driving/braking force generator. The controller calculates a target inter-vehicle distance between the preceding vehicle and the host vehicle, calculates a target vehicle speed and a first target driving torque based on the inter-vehicle distance and the target inter-vehicle distance, calculates a second target driving torque based on the host vehicle speed and the target vehicle speed, generates a torque select signal based on the host vehicle speed, selects one of the first and second target driving torques as the target driving torque based on the torque select signal, matches the selected target driving torque with a previous target driving torque when the target driving torque is changed, and outputs the control signal indicative of the target driving torque to said driving/braking force generator.